Cell Biochemistry 2020 PDF

CELL BIOCHEMISTRY BIOCHEMISTRY| 2020  CELL Biochemistry explores molecular mechanisms of norm...

CELL BIOCHEMISTRY BIOCHEMISTRY| 2020  CELL Biochemistry explores molecular mechanisms of normal cellular processes as well as diseases. All higher living organisms including humans are made up of cells. Two major classes: Prokaryotes Eukaryotes Photo from Textbook of Biochemistry for Medical Students OLFU|BIOCHEMISTRY  HISTORICAL NOTES Robert Hooke was the first person to use the term “cell”. He referred to the small empty chambers in the structure of cork as cells. Matthias Schleiden and Theodor Schwann concluded that all plant and animal tissues were composed of cells. Rudolf Virchow proposed the theory of biogenesis where cells only arise from pre- existing cells. Cell Theory A cell is the basic structural and functional unit of living organisms. So, when you define cell properties, you are in fact defining the properties of life. The activity of an organism depends on the collective activities of its cells. According to the principle of complementarity, the activities of cells are dictated by their structure (anatomy), which determines function (physiology). OLFU|BIOCHEMISTRY EUKARYOTIC CELL vs. PROKARYOTIC CELL EUKARYOTES PROKARYOTES DNA is found in the nucleus of the DNA is not enclosed within the cell. membrane. Contain membrane-bound organelles which include Lack membrane-enclosed organelles mitochondria, endoplasmic reticulum, and Golgi complex Cell division involve mitosis. Usually divide by binary fission. OLFU|BIOCHEMISTRY  MOLECULAR COMPOSITION OF CELL Water accounts for about 70-75% of the weight of the cell. Organic compounds accounts for 25-30% of the cell weight. They are nucleic acids, proteins, polysaccharides (carbohydrates) and lipids. Proteins accounts 10-20% of the weight of the cell. Inorganic compounds account for the rest of the cell weight. OLFU|BIOCHEMISTRY  EUKARYOTIC CELL Photo from Burton’s Textbook Eukaryotic cells have a membrane-bound nucleus and a number of other membrane-bound subcellular (internal) organelles, each of which has a specific function. OLFU|BIOCHEMISTRY  PLASMA MEMBRANE Structure: Phospholipid bilayer containing cholesterol and proteins and some carbohydrates; forms a selectively permeable boundary of the cell. Functions: Acts as a physical barrier to enclose cell contents; regulates material movement into and out of the cell; functions in cell communication OLFU|BIOCHEMISTRY  NUCLEUS Structure: It is enclosed within a double membrane called nuclear envelope; contains nucleolus Nucleolus: It consists of RNA and proteins which functions in ribosomal unit assembly. Nucleoplasm: It surrounds the chromatin and the nucleoli. Function: It contains the DNA that Photo from Textbook of Biochemistry for Medical Students serves as the genetic material for directing protein synthesis. OLFU|BIOCHEMISTRY  CYTOPLASM Structure: This can be seen between the plasma membrane and the nucleus where the other cellular elements are embedded. Organelles are membrane-bound structures which carry out specific metabolic activities of the cell. Cytosol provides support for organelles and serves as the viscous fluid medium. Function: It is responsible for various cellular processes. OLFU|BIOCHEMISTRY  MITOCHONDRIA Structure: Double-membrane-bound organelles containing a circular strand of DNA Outer membrane is highly permeable to small molecules, due to the presence of a pore-forming protein called porin. Intermembrane contains many proteins that participate in oxidative phosphorylation. Inner membrane has multiple folds projecting inwards, called cristae. Function: It is responsible for the Photo from Textbook of Biochemistry for Medical Students production of energy in the form of ATP. OLFU|BIOCHEMISTRY  LYSOSOMES Structure: Spherical shaped membrane bound organelles formed from the golgi apparatus; contain digestive enzymes The fluid inside lysosomes is much more acidic, at about pH 4.8, than the normal pH of about 7.0– 7.3. Function: Digest microbes or materials by the cell OLFU|BIOCHEMISTRY  ENDOPLASMIC RETICULUM It is further subdivided into: Rough endoplasmic reticulum Structure: Extensive interconnected membrane network that varies in shape; ribosomes attached on the cytoplasmic surfaces Ribosomes are involved in the protein synthesis. Functions: Modifies, transports, and stores proteins produces by attached ribosomes Smooth endoplasmic reticulum Structure: Extensive interconnected membrane network lacking ribosomes OLFU|BIOCHEMISTRY  GOLGI APPARATUS Structure: Series of several elongated, flattened saclike membranous structures. Functions: Modifies, packages, and sorts materials, that arrive from the endoplasmic reticulum in transport vesicles Vesicles transport cellular material. Mature vesicles are called secretory vesicles. OLFU|BIOCHEMISTRY  PEROXISOMES Structure Similar to lysosome Functions It contains enzymes involved in the metabolism of hydrogen peroxide OLFU|BIOCHEMISTRY  CYTOSKELETON Cytoskeleton Structure: Organized network of protein filaments Function: Maintains integral structural support and organization of cells Microfilaments maintain cell shape. Intermediate filaments give mechanical support to structures like nucleus and plasma membrane. Microtubules provides structural support. OLFU|BIOCHEMISTRY  IMPORTANT NOTES IN PROKARYOTIC CELL Prokaryotes (Eubacteria and Archaebacteria) are the most abundant organisms on earth. A prokaryotic cell does not contain a membrane- bound nucleus. Each prokaryotic cell is surrounded by a plasma membrane. The cell has no subcellular organelles, only infoldings of the plasma membrane called mesosomes. The deoxyribonucleic acid (DNA) is condensed within the cytosol to form the nucleoid. Some prokaryotes have tail-like flagella. OLFU|BIOCHEMISTRY  CELL MEMBRANE TRANSPORT Passive Transport Process Diffusion is the movement of a substance from an area of its higher concentration to an area of its lower concentration. Simple diffusion is the type of diffusion of dissolved solutes through the plasma membrane Facilitated Diffusion is the type of diffusion that requires a protein carrier. Osmosis is the diffusion of water point across a selectively permeable membrane. OLFU|BIOCHEMISTRY  CELL MEMBRANE TRANSPORT Passive Transport Process Diffusion is the movement of a substance from an area of its higher concentration to an area of its lower concentration. Simple diffusion is the type of diffusion of dissolved solutes through the plasma membrane Facilitated Diffusion is the type of diffusion that requires a protein carrier. Osmosis is the diffusion of water point across a selectively permeable membrane. OLFU|BIOCHEMISTRY  CELL MEMBRANE TRANSPORT Active Transport Process This type of cell membrane transport uses energy (ATP) provided by the cell. For example, cell has low intracellular sodium; but concentration of potassium inside the cell is very high. This is maintained by the sodium– potassium activated ATPase, generally called as sodium pump. Exocytosis refers to bulk movement of substance out of the cell by fusion of secretory vesicles with the plasma membrane. Endocytosis refers to bulk movement of substance into the cells by vesicles forming at the plasma membrane. OLFU|BIOCHEMISTRY ACTIVE TRANSPORT OLFU|BIOCHEMISTRY ENDOCYTOSIS and EXOCYTOSIS OLFU|BIOCHEMISTRY  CEL LIFE CYCLE Interphase It is the longer phase of the cell cycle where the cell is active and preparing for cell division. The DNA molecule is duplicated exactly in a process called DNA replication which occurs toward the end of the interphase. Cell Division Cells arise from the division of other cells. Mitosis consists of four stages-prophase, metaphase, anaphase, and telophase. The result is two daughter nuclei, each identical to the mother nucleus. Prophase- each chromosome consists of two chromatids joined at the centromere. Metaphase- chromosomes align at the center of the cell Anaphase- chromatids separate at the centromere and migrate to opposite poles. Telophase- two new nuclei assume their normal structure, and cell division is completed, producing two new daughter cells. OLFU|BIOCHEMISTRY MITOSIS OLFU|BIOCHEMISTRY  REFERENCES Mescher, A.L. Junqueria’s Basic Histology, 13th edition. McGraw-Hill Education, 2013, (pp. 25-72). Rao, M.N. Medical Biochemistry, 2nd edition, New Age International Publishers, 2006, (pp. 1-9). Engelkirk, P.G. and Engelkirk, J.D., 9th edition Microbiology for Health Sciences.. Lippincott Williams& Wilkins, 2011, (pp. 25) OLFU|BIOCHEMISTRY